WPF Combo box two columns in dropdown, but only the first column value when selceted

Hi,

in wpf I have a combo box which has two columns. Below is the data template used.

HTML Code:

---

<ComboBox.ItemTemplate>
                                        <DataTemplate>
                                            <StackPanel Orientation="Horizontal">
                                                <TextBlock Text="{Binding UserID}" Width="75" />
                                                <TextBlock Text="{Binding UserName}" />
                                            </StackPanel>
                                        </DataTemplate>
                                    </ComboBox.ItemTemplate>

---

When I make a selection, I only need to show the UserID.. how do I achived this?

Many Thanks